1. Field of the Invention
The present invention relates to an organic light emitting display (OLED), and more particularly, to fabricating passivation layers for an OLED.
2. Description of the Related Technology
Recent rapid development in the information technology (IT) sector has fostered rapid growth in the display industry. A display device like a conventional CRT is not suitable for new IT media since it lacks mobility due to limitations of its size, weight, power consumption, resolution, and the like. Accordingly, conventional CRTs are being replaced with flat panel displays including thin film transistor liquid crystal displays (TFT LCDs), plasma display panels (PDPs), and organic light emitting displays (OLEDs).
Among flat panel displays, an OLED is advantageous as a moving picture display, regardless of the device size, because it has fast response speed of about 1 ms or less, low power consumption, and is an emissive display and thus has an unrestricted viewing angle. In addition, the OLED has attracted attention as a new generation flat display because it can be fabricated at low temperature using conventional semiconductor fabrication techniques.
The OLED comes in an active driving type and a passive diving type which have different driving methods. The active driving type OLED is equipped with an array including thin film transistors.
The thin film transistors may need to have a high S factor to improve the grayscale display capability and a high mobility to effectively drive a circuit. In a pixel region of the OLED, the higher the S factor of the thin film transistors, the more finely its current capacity can be controlled with respect to an applied voltage, and thus the more precisely the grayscale can be expressed. In a circuit region of the display, the higher the mobility of the thin film transistors, the more favorable on-off control becomes and the faster the response speed in response to a display state becomes, which improves display quality.
However, when the thin film transistors of the circuit and pixel regions are fabricated simultaneously on one substrate, for example, in a system-on-panel (SOP), it is difficult to simultaneously increase both the S factor and mobility of the thin film transistors. While the mobility of the thin film transistor in the circuit region can increase owing to a hydrogen passivation effect, the S factor of the thin film transistor in the pixel region may decrease, and thus the grayscale display capability may deteriorate.